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How does a fighter “thump” an intercepted aircraft?
In P&E Never Again: A Thump on Final, commercial pilot Mike Mercer describes an encounter with an F–16 shortly before rounding out to land.

Without warning, the Baron abruptly yawed 15 degrees right, and there was a thunderous noise on the right side of the aircraft. I was standing on the rudder pedals to maintain directional control and managed to keep things more or less aimed at the runway … On the rollout I got a look at the F–16 in full afterburner climbing back to altitude and turning to circle the field. I concluded immediately that we had been “thumped,” a procedure we used in the military that was designed to rattle and harass the pilot of an intercepted aircraft.

For context according to the linked account, this incident took place inside a VIP TFR that the author flew into unwittingly. His hand plotting and ADS-B display on his EFB led him to believe the TFRs were well north of his destination. Shortly after departure, the author attempted to request but was unable to obtain flight following.
What maneuver does an intercepting fighter perform to “thump” its target? Other than the severe yaw that the author mentioned, what are other typical aerodynamic effects?

I can't see the military endorsing mid-air collisions with very expensive fighters as a method of harassing another aircraft. I call BS on the story. The only thing I can think of is that he got in the wake turbulence.

I assume the term “thumped” in the linked AOPA story is figurative, not a literal collision.

Similar incident with a Turkish F-16 with afterburner passing in front of a Greek F-16. The Greek pilot curses at the other pilot and briefly doesn't respond to commands. Whether he was shocked by the near-collision or stability loss that supposedly might have occurred, I don't know.

Business Insider: "Russian Su-27 fighter captured blasting afterburners in dangerous intercept of a US Navy plane", video

I just listened to this same podcast and was wondering what "thumping" meant. Glad you already asked!

'Thumping' is an (unofficial) term for maneuvering the aircraft so that the other (target) aircraft is caught up in its wake. As a practice, it seems quite widespread, atleast during cold war scenarios, and is explained elsewhere:

Aircrews call it “thumping” — the aviator’s version of a baseball hurler’s brushback pitch. A fighter jet zooms up behind a lumbering reconnaissance craft, then blows past with afterburners blazing, pulling up and away just in front of the larger plane so its jet wash disrupts the airflow around it.

The effect is the same as flying into other aircraft's wake turblence, though the effects may not linger as long as the aircraft passes quite fast (that being the idea- to harass, rather than to cause an accident).
That said, I doubt it was done deliberately in this case as it is quite dangerous to both the aircraft and intercept procedures are quite clearly defined.

Intercept procedure; from FAA media release
Note that it specifically states to be cautious of wake turbulence. Maybe the author got caught in the wake turbulence of the fighter accidentally and it brought back memories of his service days.

Not just cold war. It happens even today among nations that aren't at war (yet).

In a thump the jet positions itself slightly in front of, and under one wing. Works well on a prop aircraft, as the airflow is disrupted across the wing, making the plane fall, rather abruptly, 20 to 60 feet. Once it is clear of the wash, normal flight resumes.  However, the jet can reposition itself again, for another thump.
There is little risk to the aggressor in this case.
Addendum #1
From an ABS news interview, http://abcnews.go.com/Nightline/story?id=128859&page=1

Q: Isn't there a certain amount of gamesmanship going on at least in
  your experience with the Russian pilots?
A: There was. Most times it was a very straight-forward operation.
  They would come join on us, see that we were the same airplane that
  was out there the day before probably, and then leave. Every once in
  awhile they would get a little closer, stay a little longer and on two
  occasions they did what we call a thumping maneuver — where they'd
  come up underneath us and then pop up in front of our nose and put us
  into their wing tip vertices and their jet wash and bounce the
  airplane. And one time they bounced so much that the auto pilot kicked
  off and we started to make a turn that we hadn't planned on and we had
  to quickly react to that.
Q: This thumping occurs when they are flying right underneath your
  aircraft and then pull up in front of you?
A: Yes. What they do is they come up right underneath your aircraft
  and then pull up right in front so that the wing tip vertices and the
  turbulence from their wings and their engines go right in front of the
  airplane and get the fuselage and wings of the P3.

From the book, The Chinese Navy: Expanding Capabilities, Evolving Roles
edited by National Defense University (U S ), Institute for National Strategic Studies, Phillip Charles Saunders, Christopher D. Yung, Michael Swaine, Andrew Nien-Dzu Yang

“In a spiraling exacerbation of tension, the Chinese became
  increasingly reckless in their responses to American reconnaissance
  missions. PLA Navy Air Force (PLANAF) pilots began harassing American
  pilots, either as ordered from above or on their own volition, often
  employing alarming closure rates during intercepts and sometimes even
  pulling ahead of the larger aircraft and “thumping” it with engine
  afterburner exhaust. (*26) Finally, on that fateful April Fools' Day
  2001, “hot-dogging” Lieutenant Commander Wang Wei captured the world's
  attention when he struck a U.S. Navy VQ-1 EP-3E on his botched attempt
  at a third “join-up.” … The pilot of the EP-3, young U.S. Navy
  Lieutenant Shane Osborn, recovered from a steep 8,000-foot
  uncontrolled dive and flew toward Lingshui on Hainan Island in his
  badly damaged aircraft (*27) Osborn made an engine-out, no-flap
  landing without an airspeed indicator at the PLA Navy airfield...”

And this from Congressional Research Services, Order Code RL30946, China-U.S. Aircraft Collision Incident of April 2001: Assessments and Policy Implications

On several occasions, PLA pilots had overtaken EP-3 aircraft from
  the stern at high speed, passing underneath and abruptly pulling  up
  in front of the American aircraft at close range. The practice known
  in some pilot circles as "thumping" is essentially an aerial tweak,
  intended to cause consternation to the victim as he is suddenly
  confronted with the noise, jet wash, and the jet in unexpectedly close
  proximity.

Normally thumping does not make the media, but in 2001 an incident involving the EP-3 suffering significant airframe damage elevated this to public light. While journalists, media and other non-pilots may comment on thumping and simplify it to be wake-turbulence, or whatever, it should be clear that the thumping maneuver is intended to induce loss-of-control, even if only temporary, on the victim aircraft.
Furthermore, contrary to press reports, the maneuver is more effective when performed asymmetrically on the victim aircraft, as it can induce a unilateral stall-spin due to the loss of lift on one side of the wing, which increases the "effectiveness" of the maneuver.
A former USAF one-star indicates that more than once he had fleet airframe damage and had to remind pilots to avoid doing such maneuvers during training sessions. He also indicates that there is no SOP or written guidance on this procedure, as of his retirement in 2006.
In summary, thumping is not a normal wake turbulence maneuver. It is not a ICAO style intercept maneuver. Executed asymmetrically, this deliberate maneuver has a very significant aerodynamic effect in that it causes loss of lift on one (or more) wing, unexpectedly.  While on low approach, it is extremely risky. The maneuver is not documented as a standard maneuver, nor is it officially sanctioned. There are numerous memos discouraging or prohibiting the practice of the procedure. A Vietnam era F-4 pilot recalls the maneuver being used in Vietnam, but does not know when it was first employed.  He points out that the capability of the F-4 and other Vietnam-era fighters facilitate the maneuver.

I'm not questioning your answer, but do you have any sources about thumping? The specific scenario in the question seems unbelievable (deliberately endangering an aircraft on short final) but for all I know, thumping as a general maneuver might still be a standard practice in other circumstances.

Most of the guys I work with are former Air Force.  I don't think it is in a SOP manual.

Any actual data on this would be great.  Sounds like nonsense to me.  It would be super easy for the victim to alter course and avoid the "thump."

Published data, or experiene? Co-worker who flew F-4s in Vietnam and was career officer, had first hand experience. Says it was common practice when intercepting recon flights in international airspace. Not condoned, but done. Co-worker who flew U-2s and was base commander at Beale was familiar with the procedure. Process is different than simple wake turbulence, as if it is done right, it causes loss of lift on one (side) wing, creating a substantial loss of control to the victim aircraft. Keep in mind that the aggressor comes from below, out of visibility, and attention may be elsewhere.

The description in your first paragraph doesn't seem to match any of the others here, at least in my mind.

@mongo, a second hand story does not equal first hand experience.  Nearly two decades of flying has led me to the conclusion that pilots just might, possibly, maybe embellish stories to punch up the entertainment value.  Yes, I'm sure your contact is a right proper jet jock ace but I too have met enough  officers who have told me amazing stories that defy belief.  Funny thing is that they are always impossible to verify!  Wake turb I get (I think we're talking about wake turb here, which I know first hand to be a thing).  A special lift deleting air force secret sauce...hmm.

@mongo There have been recent reported incidents. Please check my comments underneath the question. (That was just a quick search. I'm sure there are other videos of similar incidents.)

@Fermiparadox, thanks for the reference.  This maneuver has been used for quite some time, and a few aircraft have been lost when it was done on final approach.  Friendlies have done it to each other.  Just because it is not well documented, or there is not an AF or Navy SOP for it, doesn't mean it isn't a regular practice.  Obviously others have the maneuver in their repertoire, per the article you reference.


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How far can airplanes glide?
On an another question, an answer said:

You don't need an engine to fly as airplanes are designed to glide without it.

I suspect this heavily depends on the type of the aircraft, so lets assume we are considering a small airplane.

How far could an airplane glide?
What governs the glideability of an airplane?
Is it possible, for an airplane with an engine/engines, to leverage this to save fuel while flying, or are they too heavy/otherwise unable to do this?

glideslope and initial altitude will be the key words

As a glider is also an airplane, if the weather is right, the upper limit is only limited by pilot endurance.

@HorusKol all aircraft can glide some distance. What that distance is depends on aerodynamics, atmospheric conditions, initial speed, and weight. And of course pilot skill.

Another example of an airliner gliding is Air Transat 236 -- around 120km in an Airbus A330 in 2001.

Motor gliders can do just that, depending on type and pilot´s preferences: switch off the motor and use e.g. thermals or other updrafts. For gliders with retractable prop, this is the standard way to fly for >98% of the time.

For gliders, this site claims an endurcance record of bit more than 56 hours. The discipline was cancelled later on due to inherent dangers and stricter regulations (and rightfully, too). Nowadays you are only allowed to fly a glider from sunrise to sunset (at least in Western Europe).

Very aircraft dependent. From the F-111 flight manual: Double engine out: step 1) Eject. (To be fair, that's only after a failed attempt to restart one engine.)

@TUMBLEWEED, you may be right, but it makes for a great punchline!

@yankeekilo So go above the arctic circle in the summer and compete.

@d-b huh, sounds too cold for me (but let me know how it goes) :D

I suspect this heavy depends on the type of the aircraft, so lets assume we are considering a small airplane.

Absolutely right, it does vary widely. The parameter you're asking about is called glide ratio and it is directly related to another parameter called lift-to-drag ratio or L/D ratio. This is a fundamental characteristic of the aerodynamics of a particular aircraft. L/D ratio varies with airspeed; for determining best engine-out glide performance, the L/D ratio at "best glide airspeed" is used. "Best glide airspeed" is the speed that maximizes the L/D ratio, and this maximum value is known as L/Dmax.
The maximum L/D ratio (L/Dmax) of a Cessna 172 is about 9, so its glide ratio is about 9:1 - for every 9 units traveled forward it will lose 1 unit of altitude. So, it will glide about 9,000 feet for every 1,000 feet of altitude available. This is a fairly typical value for small planes.
To show you how widely variable this is, a modern glider can achieve ratios above 60:1, while the Space Shuttle ranged from about 1:1 at high speed, early in reentry, to 4.5:1 on final approach.
Notably, large transport aircraft tend to have significantly higher L/D ratios than small aircraft: a 747 can achieve an L/Dmax of about 17:1. With an altitude of 33,000 feet (~10,000 meters) that would mean a gliding distance of 100 miles (~170 Km).

What governs the 'glideability' of the plane?

As above, its lift-to-drag ratio. Very casually speaking this is just a measure of how "aerodynamic" the airplane is, comparing its capability to generate lift with the drag it creates in the process. The better its lifting capabilities, or the less drag it generates, the higher the ratio.
For more information, I highly recommend a free online book on aerodynamics called See How It Flies by John Denker. It is written for pilots, not mathematicians or physicists, so it explains the concepts very intuitively without a lot of equations. It talks about L/D ratio and explains some of the factors that affect it. (I would recommend this book to any pilot anyway.)

Is it possible, for an airplane with an engine/engines, to leverage this to save fuel while flying, or are they too heavy/otherwise unable to do this?

Since glide ratio is directly related to (indeed it's the same thing as) L/D ratio, you could say that airplanes already do take advantage of it. The higher their L/D at cruise airspeed, the more fuel-efficient they will be (because less thrust will be required to counteract drag in steady-state flight).
If you're asking about shutting the engines off during approach/landing to save fuel, there is another question here on ASE which specifically addresses this. (The answer, in short, is no, it's not practical.)

Worth mentioning: as dvnrrs says, the L/Dmax airspeed is the "best glide" speed. Pilots memorize the best glide airspeed for their airplane, and if the engine craps out, we're trained to immediately go to that airspeed by raising or lowering the nose (usually raising) to maximize our glide. It also turns out that if you want to maximize the range you can fly on the fuel you have, you would also fly at that airspeed. In my plane, you can reduce the fuel consumption from 9.5 gph to 5.5 gph by flying at best glide speed, but it's a bear to maintain that speed, so you don't do it very often.

2dvnrrs, the figure you post for the 747 is likely with engines idling? With four shutdown engines I would be really surprised if it could achieve such glide ratio.

@MartinArgerami You may be right; my source was the linked Wikipedia article. If someone has more official figures for a typical large transport I'll update accordingly...

I have checked a little more, and it looks like you are right; it is the glide ratio with engines off.

At the moment the upper limit for glider L/D is around 65 to 68, see e.g. the EB 28 and EB29. 60s are not too uncommon for open class gliders.

btw, if it was an engine-out rather than a fuel-out situation, would you start dropping fuel instantly to reduce weight hence the gravitational force?

@yo' maybe. That would probably make a good full-blown Question in itself. Factors include (a) time available (are all engines out?); (b) ability to dump at all -- only some aircraft types have this capability; (c) location near an appropriate dump area like an ocean; and (d) necessity -- is the aircraft above its maximum landing weight and/or are there other problems like landing gear issues that would make it desirable to sacrifice time for reduced landing weight. Generally in an engine-out scenario you would want to get back on the ground ASAP unless there's a very good reason not to.

This is misleading: the Space Shuttle ranged from about 1:1 at high speed, early in reentry, to 4.5:1 on final approach. The Shuttles, like all other aircraft, have one L/Dmax, but you can certainly fly below that.

the glide airspeed also depends on what you want to do: either glide the longest distance or stay aloft the longest as per: http://www.5c1.net/Glider%20Performance%20Airspeeds.htm . and if you want to glide the longest distance, heavier weight airplanes glide longer.

@dvnrrs Why do you need an "appropriate dump area" to dump fuel, surely it will vapourise rather than fall to the earth as rain?

@Calchas: Quite a bit could be written about dumping fuel. It would be worth posting as a question.

To give some concrete examples:
A Cessna 172 might fly at 2000 ft for a short hop, or at 12500 ft for a longer cross-country flight. My rule of thumb is about 1.5 nautical miles glide per 1000 ft altitude above ground level, thus:

From 2000 ft, a Cessna would be able to glide about 3 nautical miles (3.5 statute miles, 5.5 km), and it would take about 3 minutes for that.
From 12500 ft, just in proportion, it would be about 18 nautical miles (21 statute miles, 33 km), giving the pilot an ample 18 minutes to troubleshoot, find a suitable landing spot, and communicate the predicament.

A big jet flies higher during cruise, say at 38000 ft, and has a better glide ratio.

From 38000 ft, a jet might glide for 75 to 100 nautical miles (140 to 180 km), and take about 20 minutes to do so.

Glide is measured in what's called "glide ratio". For every foot of altitude the airplane loses, how far forward can it go? Sailplanes (gliders) have a glide ratio around 40 to 1. It can be much more or less, depending on the model. The glide ratio of the Cessna 172, the most popular single engine airplane, is about 10 to 1. The Boeing 767 that lost all power attained a glide ratio of about 12 to 1 in practice.
Airplanes generally do not use this to save fuel. It's much more efficient just to fly the airplane normally, or at low power if they are looking to conserve fuel. To glide would require turning the engine on and off. That is not efficient in jets, turboprops or piston engines. I believe some unmanned, high altitude aircraft may turn their engines off, though.

For what it's worth - the particular 767 incident referenced in this answer was the Gimli Glider.

@dvnrrs However, the Gimli hero had the other problem in the end: he needed to slow his huge aircraft so that it doesn't crack on touchdown. He managed in a way unseen :-)

Glide distance does indeed depend heavily on the airplane's characteristic glide ratio, which depends on airspeed, as the answers above describe.  However, the answers above assume still air, and real air is never still.
If you glide with a steady tailwind, you'll glide further than you will in still air; a steady headwind will cut your glide.  (You'll get the same sink rate and therefore the same time aloft, but you'll make a different amount of distance over the ground.)  If you're at altitude, it can be difficult to tell which way the wind is blowing unless you already know or unless you have a GPS so that you (or it, automatically) can compare your speed across the ground with your speed through the air.
Also, downdrafts will cut your altitude and thereby your glide distance; but updrafts will do the opposite.  As a matter of fact, in the right kind of weather pilots who are trained to find updrafts--glider pilots, for example--can stay aloft without power for as long as they like.  Updrafts are in general powered by the sun, though, so after dark it gets difficult to find "the right kind of weather."  Also, updrafts tend to be localized and fairly stationary, so flying circles to stay in one, if it's weaker than you expected, may use up more of your gliding time than it adds and so reduce the total distance over the ground that you can glide.

yes, asked and answered

Powered light aircraft can make sustained flight with engines off when their flight path aligns with hill or mountain ranges receiving steady wind on one face. In certain environments and weather conditions these ranges generate Wave lift that is substantial enough to allow high speed flight at altitudes exceeding 20,000ft in silky smooth conditions over many 1000s of kilometres. Associated with these conditions are extreme rotors outside the band of lift. Sailplane pilots (eg Delore in NZ Dec 2009 2500km) have set world record long flights using extensive ranges that form the spine of both Islands.

I was told by a pilot that he flew for some time over the Pirineos mountains with a Spanish version of Junkers Ju-52 with engines idling, and maintaining height on a hot air ascending current, as sailplanes do, but probably it's an exception rather than any rule.
Literature about Sud-Aviation's Caravelle discussed also a 'gliding' flight of some hundred kilometers, starting at a very high altitude and in special experimental conditions, taking place before 1964.
A pilot won an award after landing a jet airliner with engines not running; when he was approaching an abandoned airstrip, he realized that height was too high, he put the airplane in a crossed control surfaces pattern to slide on the side and lose altitude.
Others flew for a while a DC-3 in inverted flight from Gando, in Gran Canaria, to Lanzarote, also in the Canary Islands, just to find on landing that engine nacelles were covered by oil, as the DC-3 engines lacked an inverted flight crankcase or 'dry' oil carter. One of the men in this DC-3 flight, Fernando Aymerich-Alix, bellied a Sabre or Super-Sabre jet fighter in a plowed field, on the premises that he felt the indications of fuel tank gauges were inaccurately high, and he will soon run out of fuel. When reaching the ground, the somehow abundant fuel actually left in the tanks spread as a shower all over the airplane and the place, he was lucky the fuel didn't catch fire. He died first half of December 2017

Hello user3424, welcome to Aviation.SE. Do you have any citation or sources for your examples above, e.g. a reference to the Sud-Aviation Caravelle ads or the DC3 inverted flight?

Sorry, I can't, it was a personnal communication, in the Ju-52 and DC-3 cases, the Ju-52 pilot is dead, and for the Sud-Aviation Caravelle gliding, its from articles in non-technical press of its days, perhaps the heirs of Caravelle makers can told you about this. The pilot of jet airliner forced landing because of an engine failure (out of fuel because a mix between imperial and metric units?) received a Civil Aviation Award, it must be recorded somewhere, the issue is that I don't have academic pretensions, so, I can't always provide with accurate references, as I don't hold files about it.

The jet airliner gliding, and doing something to lose altitude, sounds like the Gimli Glider.

Yes, it was this Gimli Glider case I was referring to, thanks for your help. By the way, I was told about a windshear incident at Chicago (O'Hare?) airport, where an Spanish DC-10 crashed with only not too heavy lesions for an air stewardess, and slight airplane damages, pilot was the late: 'Chus Calderon'; when the FAA attempted to simulate the incident, even when they knew what would happen, in every simulation the end was a total loss of aircraft and lives. I failed to locate this event in the DC-10 or airplane crashes databases.

To SentryRaven: one of the men on board the DC-3 that flight a while 'inverted' died recently, so I can tell you about his identity: Fernando Aymerich-Alix, the departing Airport was Gando, in the Island of Gran Canaria

"Glideability" is flight. A fixed wing aircraft that is controllable under power, is controllable without it. Some aircraft are specifically designed to be unstable in flight, such as the F-16, and F-117. in those cases computers assist to provide artificial stability; as long as the computers are working, the aircraft is still controllable without a functioning powerplant.
Glide ratio varies significantly between fixed wing aircraft. Unpowered gliders are generally higher than 20/1, while many small planes see 17/1 or less. The space shuttle is 4.5/1. (Horizontal/Verticle)
Glide efficiency is mostly a function of drag, not weight. For example:  gliders sometimes carry water ballast to increase weight, since higher weight results in higher glide speed. (The water is dumped to slow the aircraft before landing.)
The FAA publishes airmans manuals, and you can find a variety of other flight instruction manuals available online or at the local airport. Any Private Pilot or Sport Pilot manual will discuss the basic principles of flight in some detail, They usually make for very clear and easy reading.

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Are ICAO and FAA airport signs and markings the same?
Are ICAO and FAA airport signs and markings the same or are there differences? If so what are the differences?

Here are the FAA sign standards

This question seems very broad. The full list of airport signs and markings is extensive; if the answer is NO—they are not the same—then an exhaustive comparison would likely be too broad for this exchange. I am not voting to close, as yet, but I think you would do well to narrow your question's scope, for example to certain signage, or to runway markings.

Thank you for your comment. I was hoping to find something similar to this but for ICAO ... https://www.faa.gov/airports/runway_safety/news/publications/media/QuickReferenceGuideProof8.pdf

Reference this Jeppesen document

Principle
ICAO Airport markings are defined by ICAO in Annex 14 of Chicago Convention, Aerodromes.
ICAO also requires at section 5.8 Notification of differences in the AIP of Doc 8126 Aeronautical Information Services Manual, that differences are explained in the country AIP, Section GEN 1.7 Differences from ICAO Standards, Recommended Practices and Procedures.
US regulations are not entirely compliant with ICAO SARP, and differences exist for airport marking.
Example of ICAO SARP
For the touchdown zone lights, ICAO states in Annex 14, at paragraph 5.3.13.2:

The lateral  spacing between the innermost lights of a pair of
  barrettes shall be equal to the lateral spacing selected for the
  touchdown zone  marking. The longitudinal spacing between pairs of
  barrettes shall be either 30 m or 60 m.

US example
As US regulations are not fully compliant, the differences are explained in GEN 1.7 of the US AIP, page 129:

U.S. does not require the lateral spacing of touchdown zone lights
  to be equal to that of touchdown zone marking when runways are less
  that 45 meters wide.

In general
All differences can be found at this location, sorted by ICAO reference and chapter. Differences related to Annex 14 start on page 124 (actually labeled GEN 1.7 81). Listing all of them (15 pages in the AIP) would be too broad for this answer.

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Why was Concorde never sold as a private business jet?
Airliners like Boeing 747 and even Airbus 380 are at times considered as personal jets for extremely wealthy people. Looking from the side, Concorde was ideal for this role: while not very big, it probably could provide luxury transportation for ten VIPs or thereabout, adding to that something that looks more valuable and more exceptional than just a "flying palace" - speed like no other. New supersonic aircraft like Aerion AS2 are often seen in this role. However, it looks like rich individuals only bought various bones of Concorde after retirement.
The fate of F-BVFD looks especially strange. As I understand, it has been retired very early, in airworthy condition, just for being a surplus aircraft. After standing for many years in the open air, it deteriorated and then has been scrapped. I cannot imagine it to cost a lot during these years of standing. Why did nobody try it for personal use? Also, some pre-production aircraft have been retired after logging not so many hours and were airworthy.
Surely, Concorde uses lots of fuel, but probably the A380 burns no much less if per flight (not per passenger). And it only could fly supersonic over sea, but was surely capable of the fastest possible subsonic flight over the land.

"Concorde uses lots of fuel but probably A380 burns no much less". Depends. are you looking at "per mile", "per hour", "per flight" or "per passenger" figures?

"was surely capable of fastest possible subsonic flight over the land" If we're being generous, then going from M.85 to even M.99 gains you about 40 m/s, or about 150 km/h. That sounds impressive, until you consider that M.85 is already in the neighborhood of 800-900 km/h. You are effectively cutting travel time by 10%, 20% at most, and you are now rather more limited in which airports you can use so it's less likely that there will be an appropriate airport near your ultimate destination, increasing travel time on the ground. That doesn't sound like a great trade-off.

Another plus would be cruising higher than other big jets, up to 60,000 ft.

@vasin1987 Good luck getting down from there to even 14,000 ft in four minutes in case of a depressurization event. 14 CFR 121.333 (e)(2). A jet that can't meet that requirement seems a lot less attractive than one that can.

@aCVn do you have a source that concorde cannot meet the said requirement?

@aCVn The part of 14 CFR 121.333 (e)(2) that mentions descending to 14,000 feet in less than four minutes only applies to aircraft flying at or below FL250, which Concorde (and every other passenger airliners) would generally not be doing. And that requirement is only if they don't have enough oxygen on board for 10% of the passengers to have an oxygen supply during all flight between 10,000 and 14,000 feet, which is required anyway for all aircraft flying above FL250. Also 121 CFR is for scheduled airline operations, not private business jets.

Regarding the comparison vs. private 747s and private A380s, the 747s and A380s (and 787s, etc.) are typically owned by VIPs who frequently need to travel very long distances. The Concorde had much less range than either the 747 or A380. While it was great for trans-Atlantic hops, trans-Pacific hops would be more problematic, requiring at least one fuel stop along the way, which would negate much of the speed advantage.

"I cannot imagine [F-BVFD] to cost a lot during these years of standing." Why can't you imagine that? Why would Air France want to sell the plane and potentially create a competitor to their own Concorde business? If you want to buy a 747, there are all kinds of airlines you could buy one from, so one airline refusing to sell wouldn't make much difference; but Concorde was only owned by two airlines. Also, you're only considering the initial purchase cost.

Unless you are the prime minister or queen of some country or a similar parvenu who can behave like you don't need to ask (and get away with it), what good is an airplane if you aren't allowed to fly it at normal cruise speed anywhere except ten miles into the Atlantic ocean? Concorde attracted such an awful lot of opposition despite a lot being done to avoid this... even neglecting catastrophic financials it was really kinda pointless running it at all.

@vasin1987  If we're talking about Concorde as a landlubber, you can't cruise at 60,000ft at subsonic speeds.  Concorde needs to go supersonic at half that altitude just to be able to climb.  For any sort of practical transport it's either ocean or bust for Corcorde (until the laws change and sonic booms over day care centers and hospitals suddenly ceases to concern people...)

Private business jets have a few requirements:

Operational costs must be within budget. The concorde is pretty expensive to run as demonstrated by the high ticketprices you had to pay for a trip on one of them. Fuel is only part of that costs; maintenance is a pretty big part of that as well.
Be able to land and take off close to where the CEO has his meeting. This means making use of small airfields with their short runways and noise restrictions. Concorde needed a lot of runway and was not a quiet plane.
Account for airfields sometimes not having fuel available or the fuel being too expensive. This may mean doing the roundtrip on a single tank or doing another short hop to an airfield with fuel.

Business jets would also mostly operate on a domestic scale. Doing mostly short hops where the concorde would not even reach supersonic cruise altitude before it's over the destination. While plenty of business jets can easily do 0.75 mach which is already 3/4 the speed of sound.

In short, the only likely market for a private Concorde is people interested in owning a Concorde as a status symbol.  That's what, a half-dozen oil sheiks and one or two airplane collectors?

@Mark Given that 20 Concordes were built and 14 entered airline service, market for 8 more is substantial. On Concorde scale, 8 is huge, contrary to how it appears.

Would have to research whether or not there are limitations on private sales due to possible military/terrorist applications.  Sort of like having your own personal nuclear submarine.  Shame they are all retired, but with cheaper and more plentiful fuel, and with respect to the ozone layer and sonic booms, they may be seen again!

plus crew and training availability. Concorde trained pilots were pretty rare, those without a solid and well paying job at BA or AF even more so. And as those airlines controlled the only training facilities as well there was no real way to change that. Of course had Concorde become the economic success it was hoped to be that'd have been different.

This does not answer the question at all. All your points are also valid for large airliners like an A380, but these planes are sometimes used by very wealthy people (think a prince, not a CEO).

#1 not a factor - the point being that maybe less individuals would've bought, but there are some for whom money really is meaningless.

@Bianfable, the operational restrictions on the Concorde are huge, and apply just as much to a prince as to a CEO.  No matter how much money you have, you can't drop the minimum runway length below 3600 meters, or travel faster than sound without generating a sonic boom.

Can you imagine screaming into the divebomb approach at London City with those four Olympus engines howling... or even better, ripping off with full reheat and scorching the bonnets off of the square mile.  No CEO in history could survive the rage press that would generate!

Maintenance would be one of the biggest reasons, I think, +1.

@Fattie 1 and 3 apply as much (or nearly as much) to 747 and 380. But #2 was very, very specific to Concorde - due to noise restrictions, you couldn't (except perhaps as a one-off specially scheduled) fly it to/from airports in the middle of the US and a lot of other places. Contrast that to 747 where it is really just a matter of a long-enough runway.

@Fattie There is no A380 "business jet". Airbus planned to offload an overweight early-build flight test model with screwed up wiring that couldn't be delivered to an airline. It required far too many changes and the sale was cancelled. But the fact that you think there's a private A380 means Saudi Arabia (and Airbus) accomplished their goals.

While it was never explicitly sold as such (although BAE would have happily delivered it as such) it was operated in such a manner on many occasions. As detailed by this former Concorde pilot, the plane regularly flew as a charter with small passenger loads of VIPs often. So even though no one ever owned it specifically for private business it served that purpose quite well.
There was also not a huge reason to own it privately for business as that was to be its main market. Glitz and glam aside, Concorde was a serious way for American and European based entities to have a face-to-face meeting on either turf and still be home for dinner. Offloading the maintenance and ownership to an airline was a nice plus.
Some people also speculate that the ultimately canceled Iranian order by the then Shah was perhaps for his personal use:

I can’t blame Iran for canceling their orders, as like most airlines
at the time, Iran Air was more a symbol of national identity, and the
Concorde’s were most certainly toys for the Shah rather than aircraft
for his people. Still, it’s a pity nonetherless.

Although they never bought the whole aircraft, Pepsi did buy the rights to paint one of the Concordes.
It's also worth noting that Concorde sales occurred mostly in the mid 1960s (approximately 24 minutes in) a time in which business aircraft were different than what we currently think of. Commercial flying was still a fancier affair than it is now and lots of business individuals flew commercial. Smaller private planes lived more in the propeller-driven space than the jet space. Keep in mind the Lear 23 had also just come out and the whole space of business/private jets was quite literally in the process of being defined. It would not be until 1972 that we would even start to see rock stars toted around in private jets. The late 1960s and early 1970s were pretty much considered the haydays of general aviation as post-war pilots were in a position to buy planes. The focus in the private market was heavily on selling single-engine piston planes.

This is the more sensible answer.  Basically the question is "If 747s, 380s, why not Concorde?"  Indeed, very large airliners were not private craft back in the 60s.

@Someone -- I'm not seeing what that last edit accomplished.  (Ditto for some of the changes in the previous edit -- re use of apostrophe for plural in "60's" etc, see last part of rule 6 here -- it was permissible-- https://www.grammarbook.com/punctuation/apostro.asp )

At the time the jet was in production private jets were still in their infancy.  The largest purpose built one was the Grumman Gulfstream II.  I have a feeling the Concorde was a bit out of the reach of all firms at the time.
In addition by the time the SST had gone into full production, it had largely fallen out of favor for noise and environmental reasons.  Concorde was also, dimensionally a big airplane with a length over 200 ft, making it awkward and unruly to maneuver at many smaller airports.  It also had a gross takeoff weight of over 400,000 lbs, again limiting what runways it can fly from.  Supersonic aircraft also don’t typically feature good short field capabilities which limits the airports you could fly a Concorde into and out of.  SUD/BAC quoted a balanced field length at STP for the Concorde of 9400 ft.  That really limits where where you can fly from.
So unpopular was the SST by 1980 that SUD/BAC had only produced a total of 14 production Concordes, all earmarked for either British Airways or Air France.  Most likely all of these factors combined together deterred even the most rabid buyer.

 the Concorde was a bit out of the reach of all firms at the time. I feel that this is the real answer. 40 years of continual growth for enterprises mean that firms and individuals are MUCH MUCH richer now

I guess you gotta ask the people who voted for it.

Another factor to consider: Aircraft require a lot of support. It's not enough to just sell a few aircraft. There's support that must be factored in - spare parts, training of maintenance crews, etc.

Note that this requires an entire support line - if a widget in an engine goes, you need the technical specialists, service crew, and manufacturing supply lines, to fix or replace  it. If those won't exist any more, or aren't economical for the aircraft still in private service, then that's the end of it.

This is not entire true, and with the Concorde even less so. Only 14 operational airframes were built and BAE/Airbus supported them for 34 years. In this case it was enough to only sell a few airframes. @Stilez That is also not entirely true. We have seen lots of unique aircraft in the private sector maintained and flown by small teams even when parts and support are long since out of the picture.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Do any airplanes really have this piece Tom Cruise is hanging onto in this movie?
The piece Tom Cruise is holding onto on this moving plane seems useless as a component, maybe even inductive of drag. Is this a real airplane component, or just a film prop?

I don't know the model of the airplane; I'm hoping maybe the shape is recognizable to some of you, or maybe it's even a "no-brainer".

I'm more worried about his fingers being strong enough to hold his body against the drag at the speed the plane must be going.

@Almo Yeah, but I couldn't include that in the question on this site. Only the component's existence was on topic. I could've asked more thoroughly on Movies SE, but I think the question got answered quite nicely here!

I totally agree with that!

@Almo fingers are not a problem for an Operating Thetan level VII, as that gives him real superpowers.

I thought it was a C-130, but I realize I was mistaken. I can't imagine what the holes are for, unless they're for lightening the aircraft. Other than that it looks like a blast deflector to keep paratroopers from slamming on the side of the plane on the way out.

The plane is an Airbus A400M Atlas, a four-engine turboprop military transport aircraft.
I'm referring to this page, and there the stunt is well described.
About the door, here's an explanation:

Visible in the released image, the A400M's new side door deflectors were added to the development aircraft fleet after initial tests with the ramp and side doors open resulted in high noise levels and turbulence inside the cargo hold, says Fernando Alonso, Airbus Military's senior vice-president flight and integration test centre.

So, while the answer is yes, that's a real plane with a real piece of equipment that the plane is actually designed to fly with, no Tommy boy wouldn't be able to hold on to it when the deflector is closed because each hole in the deflector is filled with a bump in the body to minimize drag. It would appear that they blacked out some of the filler bumps in post-production to make it appear that he could hang on, and they left some unblackened.

Just saying, he actually did hold on to it... http://www.cinemablend.com/new/How-Tom-Cruise-Did-Insane-Plane-Stunt-Mission-Impossible-Rogue-Nation-70462.html

@bkribbs Pretty impressive. I'd guess stock models of the plane have all the bumps, though.

Yep, just thought it was worth noting. :)

And here I was thinking it was an external passenger grip :o

"says Fernando Alonso, Airbus Military's senior vice-president flight and integration test centre."
Hmm, is somebody moonlighting?

@dkwarr87: Same name as the Formula1 driver, but here's the proof: https://airbusdefenceandspace.com/about-us/our-executive-commitee/

There's also this bit on the filming of that stunt: https://www.youtube.com/watch?v=afS5ks54tms

Fernando and Alonso are common names and surnames in Spain :)

Civilian jump planes often have some sort of similar (but much simpler) deflector in front of the door used for exiting the aircraft. It's not difficult to hold yourself on the plane, but a jump plane slows down when dropping jumpers, and the engines don't have anything like the prop blast of this plane. I have no idea what the blast would be like in the situation in this film, but hanging on the outside of an airplane in flight with just the strength of your hands is nothing exotic - skydivers do it all the time.
Source: almost forty years as a skydiver and skydiver pilot.

It's a blast deflector as said above, but most importantly, it's a blast deflector for combat drops. Combat drops happen under rough conditions and with speeds that can be greater than "clear-and-sunny" civilian fun drops.


text:
Why is the clearance delivery frequency included on an approach plate?
Approach plates include frequencies in the order that pilots will require them, reading from left to right.
The example below from McClellan-Palomar’s ILS or localizer/DME approach to runway 24 is a fair representative. On the far right hand side just above the overhead view is the clearance delivery frequency of 134.85.
Talking to clearance delivery prior to departure is common, but when would a pilot talk to clearance delivery on arrival? What is the purpose of including this frequency on the approach plate?

Related question (but no answer)

The FAA Aeronautical Chart User’s Guide: Terminal Procedure Publications in section “Bottom Briefing Strip (Communications Information),” page 15 in the revision effective 29 March 2018, explains:

The communications briefing strip contains communication information when available, in separate boxes, listed from left to right in the order that they would be used during arrival …

Clearance Delivery (CLNC DEL) frequencies; where a Control Tower does not exist or is part-time, a remoted CLNC DEL may be listed …

Relevant to the briefing strip in the question, this section adds

Note: Part-time operations will be annotated with a star. Check Chart Supplement for times of operation.

According to the Chart Supplement for McClellan-Palomar, the tower is indeed part time.

AIRPORT REMARKS: Attended 1500–0600Z‡ …
COMMUNICATIONS: …
    TOWER 118.6 (1500–0600Z‡)

Other use cases when having the clearance delivery on the approach plate is convenient are obtaining a new clearance during a brief stop and closing an IFR flight plan through clearance delivery, either local or remote, when the tower is closed.

This answer seems like it would make sense, but fails in practice: The combined tower/TRACON where I work is open part-time. When my facility is closed, Center takes over our main Approach frequency, and using that frequency they have communications to-the-ground at the primary airport. They do not monitor the Clearance Delivery frequency that we use during the day. But that frequency is still listed on the approach plates. ("It's so you can get a new clearance when doing a full-stop taxi-back" would still make sense though... if the ground controller is okay with you switching...)

An airman can close an IFR flight plan at airports without continuously operating towers using the clearance delivery frequency.

I don't think the first reason makes any sense. Requesting clearance for next flight on approach would violate sterile cockpit rules, would accept clearance before the crew reviewed the flight plan, and quick turn still means 40 minutes for a short-range, maybe 30 for regional, so well enough time to get the departure (filing is done by dispatch).

Jan, correct, and thanks for the clarification. I've edited my answer.

@Jan Hudec, I guess it depends on your company's definition of sterile cockpit, but communicating with ATC regarding your flight clearance would not meet most definitions I am familiar with.  The intent is to reduce or eliminate non-flight related conversation between pilots during critical phases of flight.

I think Greg Bacon’s answer is most correct. Closing your flight plan with Clearance Delivery when the tower is closed would help keep the Approach frequency from getting congested. Although, I can see a small, single-pilot certified aircraft utilizing their second pilot to receive further clearance for their next leg by isolating Com 1 & 2. Or, maybe to change their plans while in the hold after a missed approach. Could this be done when Approach is too bogged down and FSS is unavailable or the frequency unknown?

This is not universally true. Where I work, an airman can close an IFR flight plan when my facility is closed by using the Approach frequency. And yet, the daytime-use Clearance Delivery frequency appears on the approach plates.

If the aircraft is making a multi-hopped journey, then they will need a new clearance after they land.
In that case they may begin talking to clearance delivery before they land or while they are taxiing.

They could look as well at the next SID or AP map they will need anyway?

Granted, I don't have even a PPL so I'm no expert, but I'd hope my pilots are focused on this landing, not the next take off! Turn around times at the gate are never that short (at normal, US airports, anyway).

If you're departing at minimums, you may need to come around for a landing, so its probably a good idea to have handy the approach plate of the departure airport. NB: I don't know anyone who does this.

@FreeMan You are assuming all aircraft are commercial carriers. Also, the idea that both pilots need to be "focused on landing" is not really correct. One of the main points of having a co-pilot is so that you can multitask. In general, the captain does the flying and the first officer does the planning, so it would not be unusual for the first officer to be working on the next leg of the journey while the aircraft is approaching. Also, after you land you sometimes you taxi around a lot and the next clearance will be needed so you may as well start working on it.

@rbp: don't know anyone who departs at minimums, or don't know anyone who has the approach to their departure airport handy? :)


text:
How can I know if a landing exceeds the hard landing threshold for a Cessna 172S?
How does a pilot determine the difference between a firm landing, and one that needs to be written up for a hard landing inspection in a Cessna 172S?

If ground tell you to remove the pieces of your aircraft from the active, chances are you exceeded limits.

Have you checked the pilot's operating handbook to see if it has guidance on what constitutes a hard landing?

When in doubt, Shout.

Was it uncomfortable or did it hurt?
If it hurt you, it probably hurt the plane. That 500 pound engine is hanging a foot and a half from the firewall by four bolts. It's not hard to cause some damage.
Anyway, if you think it needs to be checked, just say something to the mechanic. It's not that time consuming, and it's better to be safe than sorry.

StallSpin has already mentioned the crucial point. The firewall will be damaged if the nose gear experiences an excessive shock. It can easily be inspected for deformation by removing the upper half of the cowling (looking through the hole for the oil dipstick,  even with a flashlight,  is not sufficient). The main gear is very sturdy and will probably be damaged last. Anyway, I would sugest to have a close look on it and check the overall condition. Also check the position of the tire valves.  They should be at a 90 degree angle to the tire. A hard landing can go together with brake application during touch down which could cause damage to the tires. Last but not least the oleo strut of the nose gear should be inspected. Find the clearance of the oleo strut under normal loads in the POH.

You should refer to the service manual for your specific airplane, but to give an idea,  the Cessna 172 AND SKYHAWK SERIES 1969 THRU 1976 SERVICE MANUAL says that you should look for "buckled skin or floorboards, and loose or sheared rivets in the area of the main gear support":

18-61. REPAIR AFTER HARD LANDING. Buckled  skin or floorboards, and
  loose or sheared rivets in  the area of the main gear support will
  give evidence  of damage to the structure from an extremely hard
  landing. When such evidence is present, the entire  support structure
  must be examined, and all support  forgings must be checked for
  cracks, using a dye  penetrant and proper magnification. Bulkheads in
  the damaged area must be checked for alignment,  and deformation of
  the bulkhead webs must be determined with the aid of a
  straightedge. Damaged support structure, buckled floorboards and
  skins, and  damaged or questionable forgings must be replaced.

-1 What good is the service manual to a renter pilot grappling whether or not to write it up? He has no access to that manual. Most likely neither does the front desk worker. If a mechanic is called in, then the FBO has assumed the decision making responsibility.


text:
Can I do a VFR climb-out on IFR flight plan?
Let’s suppose I wish to fly an IFR flight from KTUS (Tucson International Airport) to KFST (Fort Stockton-Pecos) for example. Given the surrounding terrain there is of course an ODP that reads as follows:

DEPARTURE PROCEDURE: Rwys 3, 29L/R, climbing right turn direct to TUS
  VORTAC …
Rwy 21, climbing left turn direct to TUS VORTAC …
Rwy 11L/R, climb heading 123° to 4000 then climbing left turn direct TUS
  VORTAC …
  ... Climb in TUS VORTAC holding pattern (hold NW, right
  turns, 128° inbound) to 9000 before proceeding on course.

That’s a pretty long departure procedure especially with the temperatures this time of year but it makes perfect sense due to the terrain.
Now since I expect the weather to be CAVOK until the MSA, I would prefer to do a VFR climb-out. In this case, would I present myself as a regular VFR traffic to clearance, ground and tower frequencies and request IFR once at MSA to Center, or would I request an IFR clearance on ground and add the request for VFR climb-out up to the MSA?

KTUS doesn't have a VCOA, but I can think of a couple of alternatives (other people may have more). First, file a composite (VFR to IFR) flight plan. See the AIM section 5-1-7:

Flight plans which specify VFR operation for one portion of a flight,
  and IFR for another portion, will be accepted by the FSS at the point
  of departure. If VFR flight is conducted for the first portion of the
  flight, pilots should report their departure time to the FSS with whom
  the VFR/IFR flight plan was filed; and, subsequently, close the VFR
  portion and request ATC clearance from the FSS nearest the point at
  which change from VFR to IFR is proposed.

Second, depart VFR and ask for a pop-up IFR clearance when you need it. But this isn't ideal if you know that you'll be in IMC (or in the flight levels) at some point and you want to make sure your clearance isn't delayed.
Third, depart IFR and just ask ATC for whatever handling and routing you want. If weather conditions are good and there isn't much traffic, there's a good chance they'll let you do what you want. Considering the terrain, though, I wouldn't do it unless you're familiar with the area. And of course there's a chance that ATC won't allow it anyway.
Finally, although this doesn't answer the question you could just fly the ODP. I've never been to Tucson but the airport elevation is 2643' and right now the temperature is 32C and the altimeter setting is 30.10, that means the density altitude is about 5000'. And since you're departing to the east (more or less) it looks like you'll need to get to at least 11000' (IFR altitude) because of terrain, so you have to climb 8000' with limited space to do it and with reduced performance because of the high DA.
I don't know what you fly, but climb performance in those conditions isn't great in many light piston aircraft - at least if they're normally aspirated - and a climb in the hold seems like a good way to get up there safely. Of course, if you know the area well and your aircraft is up to it, then things would look different.

Thanks for the great answer ! Very complete and very helpful :)

You don't need to do any of that. Just file IFR, and ask for a VFR climb on course when you pick up your IFR clearance on the ground.

The ODP is basically a VCOA if you draw out the hold you will see you are holding directly above the airfield.
Tucson does not want you flying the ODP if they have radar contact. They will provide vectors keeping you above their minimum vectoring altitudes (MVA).  This means your course may be erratic or you may be wondering why they gave you that heading.
Another option is to depart IFR and when in contact with departure ask to go direct to your airway and you will "provide your own obstacle separation" or somethg similar to that.  That relieves ATC from keeping you above the MVAs and they will allow you to proceed on your own course to the airway.
I've been to Tucson numerous times and this is what pilots do.

Thank you for your answer :) I figured that ATC would not want an airplane to fly the ODP by default so your second option sounds good !

Or you can depart on a IFR flight plan and when airborne request a "VFR climb to ___ (terrain plus 1000 feet or 2000 in mountainous terrain or MVA).  You have now accepted responsibility for terrain clearance.  The controller will still vector you for traffic seperation.

This is actually the correct answer according to the OP's question.

When I asked some ATC folks, they said to request the VFR climb when picking up your clearance on the ground, not after you’re already airborne.


text:
What is the bag for on a passenger oxygen mask?
We may all be familiar with the part of the cabin safety briefing where they say that, in the event of a reduction in cabin pressure, oxygen masks will drop from a compartment above our heads, yadda yadda, the bag may not inflate. What is the purpose of the bag?

I made a very quick Google and didn't find much; Wikipedia doesn't answer the question. In any case, I think the site would benefit from having an answer as I'm sure it's something others are curious about.

A quick google for images lead to this page: http://www.daerospace.com/OxygenSystems/OxygenSystemContinuousFlow.php which is in  sync with Jan Hudecs answer.

Oxygen in passenger masks is either generated by oxygen generator or released from pressurized container via reduction valve. In either case it is released at fixed rate. But human breath is discontinous. So the bag acts as a buffer. You inhale the oxygen accumulated in it and then it slowly refills while you are exhaling.

so what happens if you breath "too fast" or "too slow"? Would the bag overinflate and pop if you were breathing too slow? Would you pass out from not enough oxygen if you were breathing too fast?

So, in reality, the bag will probably inflate a little bit but potentially not enough to be really noticeable?

@n00b: It will not pop, because the flap connecting it to the mask will open due to overpressure just as it does when you inhale and the mask is not pressure-tight, so you'll just waste a bit of oxygen. The amount dispensed is enough to keep anybody usefully conscious. You'd only need more oxygen if you were doing some intense physical activity in which case you'd become tired and stop before running out of oxygen so much as to pass out.

@DavidRicherby: I think it will usually be noticeable, but it will almost never be full.

@JanHudec That's not exactly true. Oxygen consumption can also spike if you become very anxious (understandable in a plane accident) and hyperventilate. Your body would be using more oxygen than the pump supplies, and you would faint (which can be dangerous).

In addition to what our friend Jan Hudec mentioned:
Wikipedia

The mask may also have a concentrator or re-breather bag that may or
  may not inflate depending on the cabin altitude, which has (in some
  instances) made passengers nervous the mask was not providing adequate
  oxygen, causing some to remove them, who thereby suffered hypoxia.

AOPA

The partial rebreather is the most common. With these, there's an
  external plastic bag that inflates each time you exhale. The purpose
  of the bag is to store any unused oxygen, so that it can be inhaled
  with the next breath.

Airliner "Dixie cups" are not partial rebreather masks, though. The bag works differently in each design.

I can't actually track down the purpose of the bag; however, the FAA Oxygen Equipment guide states that it is not for the purpose of mixing exhaled air with pure oxygen:

The phase-sequential continuous-flow mask looks similar to a general aviation re-breather. However, both masks function differently, and the phase sequential mask allows the user to go to higher altitudes. This mask uses a series of one-way ports that allow a mixture of 100% oxygen and cabin air into the mask. Exhalation is vented to the atmosphere; as a result, the bag does not inflate. [emphasis mine] This mask can be safely used at emergency altitudes up to 40,000 feet.

Because of the construction, the bag seems to act as a buffer, as Jan Hudec states in his answer.


text:
How are wooden aircraft protected from lightning strikes?
A wooden aircraft is not conductive and if a lightning hits the wood it will instantaneously ignite. How would you protect a wooden aircraft from this occurrence?

Why would it instantaneously ignite?

@Federico, because it is the most conductive path to the ground never the less? Trees are also commonly struct by lightning and they are from the same wood, aren't they?

@Federico Wood is a lot more conductive than air. And most likely in a thunderstorm it would also be pretty damp.

By polished wooden lightning rods.

@JanHudec There's no comparison between a living tree and a flying wooden aircraft. A living tree is grounded and contains large amounts of sap -- indeed, a common form of damage to trees struck by lightning is that they explode because ohmic heating boils the sap. A flying airplane isn't grounded and prepared timber contains much less water than a living tree.

I'd opine that the component that is most vulnerable to lightning in a wooden aircraft is the pilot

Current from lightning progresses in dry wood the same way it does in air: By first ionizing molecules and then turning them into plasma. Ions and plasma are indeed very conductive. Else dry wood is a very good insulator.

Once during a bad rainstorm, lightning struck a large oak tree in my backyard. After the storm I went out to look. The tree was missing a strip of bark in a path from top to bottom (~50 ft tall tree). Apparently the bark exploded off because pieces of bark were all over the yard. Where the strip met the ground, there was a crater about 1 foot wide, 1 foot deep. However, it wasn't burned and there was no sign of a fire. Moral of the story: Hollywood lies. Trees/wood do not necessarily ignite after a lightning strike. Still, I would be concerned about fuel vapors in the tank or engine.

@DrZ214 "Apparently the bark exploded off": I can understand the tree: when heated at 30,000 K, you can lose you temper.  It's 6 times the Sun surface temperature. That said, you live dangerously!

Was the DH.98 ever equipped for IFR operations? (That'd be the old wooden wonder from WWII better known as the Mosquito :)

@DrZ214 It's bark is worse than ignite!

By not flying through thunderstorms. For a small aircraft, the lightning is not the most hazardous part of a cumulonimbus (Cb) cloud system. Mature Cb clouds have huge updrafts underneath them, which can cause enough turbulence to upset most aircraft. Heavy rain and hail is also commonplace underneath Cb clouds. Even the rain can be heavy enough to damage wooden propellers and any components on your leading edge (such as the leading-edge slats found on the Tiger Moths I fly). Hail can put holes in your canvas, which are expensive to repair - if you manage to get the aircraft home at all. This turbulence and rain persists for a much longer period and across a wider area than the thunderstorm itself.
For these reasons, the chief protection against thunderstorms is by training and procedure: student pilots are taught to avoid Cb clouds when they're visible, and to plan flights to avoid areas where Cb are forecast. Weather forecasts and reports specially call out Cb clouds to help with this, and ATIS messages often warn of "cumulonimbus cloud in the vicinity of the aerodrome".
Protecting a wooden aircraft specifically against lightning is not hugely worthwhile, because it's unlikely to be able to stay in the vicinity of the Cb cloud for long enough to be at risk of a lightning strike. It just wooden happen.

"It just wooden happen." Thanks, needed a little humor this morning.

By not flying through thunderstorms. NEXT!

Additional physics-y information: trees attract lightning strikes because they are reasonably well conductive, especially the living tissue between the bark and the heartwood. Also because one end is well-grounded through its roots, which extend down to damp conductive soil. So they are natural lightning conductors.
Wood once dried and turned into timber is not a good conductor, and a plane in flight is not grounded at one end. So it's much less attractive to lightning than a living tree. A metal plane is more likely to be struck than a wooden one because it is a near-perfect conductor and offers the lightning an much easier path than through air. However, for the same reason, a lightning strike doesn't often cause any damage to a metal plane. I'd expect that a wooden plane could be downed by a lightning strike, and lightning strikes are not always closely associated with cumulonimbus clouds. Look up "positive lightning" (a.k.a. "a bolt from the blue", literal meaning thereof). This is mercifully rare. Wikipedia reports that it has downed at least one glider.
I'd also guess that a jet engine's high temperature exhaust creates something of an ionization trail behind it, equivalent to trailing some considerable length of wire behind the plane. A piston engine, much less so.

Plenty of good points! Welcome!

"a bolt from the blue" - I've seen this attributed to crossbow bolts rather than lightening bolts.  A search online appears to find that this is something people argue about.

Well, first off a wooden aircraft is not totally manufactured from wood; it does have metallic or otherwise conductive components throughout the airframe and is engineered with conductive pathways throughout the airframe for electrostatic dispersion and lightning protection as per the requirements of 14 CFR 23.1306, 25.1316, 27.1316, and 29.1316.  It is undeniable that an airplane manufactured from wood or other  materials that are good insulators would probably suffer considerably more damage to the structure from a direct lightning strike but they have been certified as to protect critical structure, fuel tanks and other components from massive electrostatic discharges.

It depends on which wooden aircraft you are talking about. Wooden aircraft were most popular before the second war and back then many did not have any metallic or otherwise conductive elements in them (except for the engine).

While @Jan is correct, the title does say "how are wooden aircraft...", not "how were, a hundred years ago, wooden aircraft..."

@LightnessRacesinOrbit, well, most wooden aircraft are almost hundred years old and they still exist, so they still are (not) protected from lightning.

@LightnessRacesinOrbit, besides, do you actually know a modern, wooden aircraft (which is not a replica)?

By not building wood aircraft
But there is a way: build them like a composite aircraft.
There are very few wood airplanes left, for one thing.  So the problem is solved by building mostly metal airplanes for past 70 years or so.
While wood planes are excellent when new (wood is strong, light, and elastic) they have a fatal flaw: they rot on exposure to moisture. (And, they are expensive to build.)
As it happens, wood planes are still built in tiny numbers, and yes, they are vulnerable to lightning.
But lightning by definition comes from thunderstorms and these must be avoided for other reasons anyway. The few handmade wooden planes that are registered these days are light planes that rarely fly in instrument conditions and so the chance of blundering into a storm cell is really low.
It would be possible to build a protected wood plane. One could laminate a conductive screen on surfaces in the same manner as used on certified glass and other composite aircraft. However, I would guess that no one has ever done that.

Wood airplanes do have steel control cables and rods, which can conduct a strike through one side of the aircraft to the other if the skin is penetrated, which is still destructive to the wood structure at that point.  Burning or fire? Possibly if the strike is strong and penetrates the right places.  That's why it's a good idea to install grounded static wicks in proper strategic trailing edge locations.
There are modern and sleek kit planes out there today.  Very sharp-looking, and pretty quick too.

There are also conductive paints that cause the skin of the plane to carry the charge regardless of its composition.
I would suspect that conductive paints that lead to static dischargers could also be used on wooden structures with cloth skins.

I very much doubt that conductive paint is going to be enough for the enormous currents that lightning strikes cause.


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What are pro/cons of steam as lifting gas for airships?
I was reading Wikipedia page about hot air airship and another Wikipedia page about the first powered and steerable airship which was powered by a steam engine. So I ask myself "why didn't they use the exhaust steam from the steam engine as lifting gas?"
After quick research, I found this home made experiment of steam used as the lifting gas. This website even gives a comparison with other lifting gasses:

+-------------+----------+------------+-----------------+--------------------+--------+-----------+-------------------+------------------+
|     GAS     |   M.W.   | Temp. (°C) | Density (kg/m3) | Lift (N/m3) in ISA | Safety |   Cost    | Ease of provision | Buoyancy control |
+-------------+----------+------------+-----------------+--------------------+--------+-----------+-------------------+------------------+
| H2          | 2        | 15         | 0.084           | 11.19              | bad    | fair      | fair              | no               |
| He          | 4        | 15         | 0.169           | 10.36              | good   | very high | very bad          | no               |
| CH4         | 16       | 15         | 0.676           | 5.39               | bad    | low       | fair              | no               |
| NH3         | 17       | 15         | 0.718           | 4.97               | fair   | low       | fair              | no               |
| hot air     | 29 (avg) | 110  (avg) | 0.921 (avg)     | 2.98 (avg)         | good   | very low  | good              | yes              |
| steam (H2O) | 18       | 100        | 0.587           | 6.26               | good   | very low  | good              | yes              |
+-------------+----------+------------+-----------------+--------------------+--------+-----------+-------------------+------------------+

(source: http://flyingkettle.com/jbfa.htm)
Given the conclusion of this website, steam should now be more widely used as a lifting gas:

it is available since the first lighter-than-air (plenty of time to develop the technology)
it has a good lifting power
it is cheap and safe

Yet, on 2020, almost all airships and balloons use helium or hot air, and no other lifting gas. So there must be drawbacks I fail to imagine. I hope finding those drawback will orient my research for my first question ("why didn't they use exhaust steam as lifting gas on airship fitted with steam engines?"). Moreover, there may be advantages I also fail to imagine.
Thus, what are pro and cons of using steam as a lifting gas?

Maybe someday we'll be allowed to use HTML tables in StackExchange sites...

@rclocher3 This was discussed many years ago and I see no reason for this to change. You may still contribute on the meta post linked in this comment.

I've seen other markdown formats that support tables nicely.  An announcement on meta.SE dated June 1st, 2020 gives reason for hope: "Once the dust has settled and we’re all comfortable with the new Markdown renderers under the hood, we can re-evaluate if the time is right to bring table support back to the (drumroll) table!"

@rclocher3 nice one, I just upvoted the meta.SE announcement.

The main disadvantage is the energy required just to get off the ground. Let's do a back-of-the-envelope calculation, comparing this to a hot air balloon.

Let's heat 1m³ of air. To get equivalent lift, we need about 0.5m³ of steam.
The density of air is about twice the density of steam. So, for a given amount of lift, we need to heat approximately the same mass of lifting medium.

To heat 1kg of air to 100°C above ambient, we need about 100kJ (specific heat of air is about 1kg/(kJ K)).

To heat 1kg of water to 100° above ambient, we need about 420kJ just to heat the water. To vaporize the water, we need an additional 2250kJ, for a grand total of 2670kJ.

The most used hot air balloon size is 2800m³. For that we need to heat 1400kg water. Multiplying gives about 4GJ of energy or 75kg of propane just to get off the ground. Since we established steam can lift twice as much per unit of volume, we can maybe get away with 2GJ or 35kg of propane.

Some more negative thinking... Condensation on the outer shell seems like a very efficient mechanism to transport heat energy to the environment, only partially offset by the reduction in surface area compared to a hot air balloon due to the cube-square law. This may require more energy in flight than a hot air balloon. Closed-cycle operation (only heat condensed water, not 'new' water) is preferred due to the high energy requirement, so descending means you have to wait for enough water to condense or be willing to pay the price in fuel. Superheated steam is not safe (despite what your table says); the high heat capacity and enthalpy of condensation can result in serious scalding burns compared to hot air. All of these effects are of course much more pronounced when comparing to a helium-filled blimp.
Still, it's a really neat idea, and sometimes you don't need a practical reason just to build something neat.

Comments are not for extended discussion; this conversation has been moved to chat.

In short, helium (or hydrogen) remains in the gaseous state at much, much lower temperatures than water does. In particular, helium or hydrogen will remain gaseous in pretty much any part of Earth's atmosphere. Water, on the other hand, will not naturally remain gaseous in any part of the Earth's atmosphere. On the contrary, it will freeze in most of the Earth's atmosphere.
For steam to remain steam, it must be constantly heated to make up for the energy it's losing by heat transfer to its surroundings. You can aid this by insulating the airship really well, but you can't bring the heat transfer down to zero. And this will also add a significant amount of weight, reducing efficiency further.
Additionally, as Sanchises's answer mentions, it takes a large amount of energy to turn that water into steam in the first place. Water has a very high specific heat and also a high enthalpy of vaporization. That is, water takes much more energy per unit mass than most substances to heat up and also more energy per unit mass to convert from a liquid to a gas.
So, you're requiring a very large amount of energy to get the water into the gaseous state in the first place and you then need a large and continuous energy source to keep it there during flight.

Re "Water, on the other hand, will not naturally remain gaseous in any part of the Earth's atmosphere.": As long as the temperature is above the dew point it will naturally remain gaseous. At any one time (on average) 0.4% of the entire atmosphere is water wapor (1% at sea level).

@PeterMortensen Well, yes, but the dew point of a steam-filled airship will be much, much higher than the local atmospheric temperature, especially at altitude. If it's allowed to drop in temperature inside the airship or to vent at any significant concentration outside of it, it will very quickly condense (and, at high altitudes and/or cold climates, subsequently freeze.) I was simplifying things a bit for the purposes of what is relevant to the question that was asked.

Lighter than air balloon works by replacing air with some gas that is lighter than air. Your steam airship would work if we can keep steam at 100 C or higher or else you risk condensation, your balloon collapse into some saggy bag and you fall out of the sky. Wikipedia mentions that when water turns into steam it expand 1700 times so imagine, in reverse, your 1700 cu.m. hot steam balloon when cool down and becomes 1 cu.m. bag of water and you lose all the lift. That does not sound safe at all. Consider low temperature up there you need a lot of energy to combat heat loss through conduction over a large surface area of the gas bag.
To sum it up you need lots of energy to keep the balloon in positive buoyancy and a big safety issue to solve when that energy source fail.

Condensation won't just cause the balloon to "fall out of the sky". The energy required for condensation has to go somewhere, and if the balloon is sealed, radiation and conduction through the balloon is the only way it can exit. As long as enough heat enters the balloon to equilibrate it, the physics work out just like an average hot air balloon.

@March Ho and if the boiler fails?  It might not be as dramatic as the collapsing can experiment but it will be more violent than if air cools.

@BlokeDownThePub and if the flame fails on a standard hot air ballon? It’s still going to be a gradual process for the ballon deflating and falling.

You seem to be thinking that the steam needs to be kept above 100 °C, because if it were to drop to, say, 99 °C, all the water would condense and you'd fall out of the sky. That's completely wrong. Going by the numbers in Sanchises' answer, steam contains an enormous amount of energy compared to hot air. The amount of heat loss which would cool hot air to room temperature (producing, I think, about a 25% decrease in volume) would merely condense 5% of the steam (a 5% decrease in volume).

So, by my calculations, in the event of a heater failure, steam would be much safer than hot air, quite contrary to your assertion that "you risk condensation, your balloon collapse into some saggy bag and you fall out of the sky".

@TerranSwett is absolutely right, the huge heat capacity of water and the even bigger condensation heat (i.e. heat that is produced when condensating, helping to stop further condensation) is a safety feature, not a problem. The problem would be that this huge heat capacity is also dangerous if you come into contact with the gas - you can probably survive for a moment inside a hot air balloon, a steam balloon would lethally burn you in seconds.

The risk of condensation is increased because temperature decreases with altitude at an average rate of 6° per 1000m.

In addition to the tremendous energy requirements, you'd need a highly specialized design that is not at all bothered by boiling hot water dripping back out of the balloon. Even if it was highly insolated, you'd need to be resupplying steam to keep the balloon inflated because even small amounts of local condensation would pull a lot of water out of the air because water expands so much when it becomes steam.
Even like, a cup of water running back down the balloon over the course of the entire voyage would be over 100 gallons of steam. This in general would be hard to build, fuel inefficient and difficult to control while being wildly dangerous.
They didn't use exhuast steam because the efficiency of a balloon isn't acheived by min/maxing the displacement of air by any means possible. It is acheived by realiability, cost and control. Blasting a second gas as a by product of the steam engine, doesn't improve that in the slightest, and likely would create problems.

That problem could be mitigated by having a bag that contains water vapor which is captive within the main air gasbag so that it wouldn't need to contain a significant pressure nor temperature gradient.

I think if you would use a doble type flash boiler wich is a light steam generator (it was even used to power a plane) and you use the envelope to condence the steam and then have it gather at the bottom to be pumped into the generator again then you can reuse the water and the envelope doesnt need to be insulated. Also the steam that comes out of a flash boiler is dry superheated steam wich is super hot and is generated instantly so as soon as it comes into the open space of the envelope it is able to expand reducing presure and temperature and so creafing lift. Much like a hot air balloon but the cold air wich in this case is water is reused again. Maybe a metal clad envelope would be better suited than a balloon because it cant deflate.


text:
Why is the fuselage on an airliner circular-shaped?
Consider the fuselage of an A300. I have noticed this not only with airliners, but also for private jets and turboprops: why is the fuselage circular-shaped? Why don't aircraft have square-shaped fuselage? Does it have to do with too much drag?

The fuselages are circular (or nearly circular) in shape for two main reasons:

The main reason is that for a circular cross section, the pressure loads are resisted by tension, rather than by bending loads in non-circular sections. Also, the non-circular sections have stress concentrations when pressurized, which may lead to failure.

In case of a circular design, the flow will not separate under small (to moderate) angles of attack and in sideslip.

In case of non-pressurized aircraft, the fuselages are dictated by volume constraints and are usually rectangular in shape as it is more efficient in space utilization.

Source: adg.stanford.edu
In the case of pressurized aircraft, the best option structurally is to have a circular fuselage, but in order to have a useful internal space, an elliptical or 'double bubble' design is used, with an outer circular section and divided internal sections, like the A380.

Source: EADS

If you pressurize any hollow structure, it will try to assume a round shape. If you want to create a lightweight pressure vessel, again a sphere will be the most efficient result, because there the stresses in the skin will be equal at every point. Blow up a party balloon if you are in doubt.
A sphere is not the most efficient shape for aerodynamics, so fuselages are elongated spheres with a nice fairing at the end. If you make them cylindrical in the middle, you can build most bulkheads on the same jig and can interchange sections of the internal fairings. Plus, if you need a longer or shorter fuselage for the next version of the plane, you can easily add or remove sections - the parts will still fit after the modification.
Note that the fuselages of unpressurized aircraft don't follow this logic A Short Skyvan or a Dornier 228 have fuselages with a rectangular cross section, so large cargo can fit in.
Also, some fuselages are combinations of cylinders. The Boeing 377 Stratocruiser used the lower fuselage of the B-29 and had an upper, larger cylinder on top to give the passengers more room.

Boeing 377 cross section (picture source)
For the same reason, rocket stages are cylindrical, too. They also need to be aerodynamic, have to tolerate high internal pressure and need to be lightweight.

+1 for answering the inverse question why some fuselages doesn't have circular cross section ? Should deserve a "true" +1 if compromise between aircraft purpose (cargo/compliant with containers specification..) and weight added (why are fuselage like those of ATRs, A380, CN235 and 737 doesn't take advantage of the extra space of a circular fuselage...)

The "will try to assume a round shape" part is due to gases' natural behavior of assuming the container's shape, which causes pressure to distribute equally in the perimeter area. If the container is flexible (think that metal is flexible given enough force) it will warp to distribute tension. A sphere distributes tension equally, whereas a cube does not. Accumulated tension requires structural reinforcement, thus weight, thus it's less economical for a plane.

Why don't [airliners] have square shaped fuselage?

Shorts Skyvan photo from Wings over Europe

Shorts Skyvan diagram from A Tall Guy
Most airliners are pressurized. If you inflate a rubber balloon you'll notice that the most economical and strongest shape for a pressurized container is one with a circular cross-section.
You'll also notice, when you inflate an Origami water bomb (you should stop reading this and make an origami water bomb now), that the flat sides buckle and bulge - flat sheets are not good at resisting pressure.
Spherical airliners would have too many disadvantages but cylindrical ones have a good balance between strength, weight, drag and space-efficiency.
As you can see above, in some circumstances, aircraft manufacturers do beleieve that the advantages of a  rectangular cross-section are worthwhile.

I personally believe in rectangle design.

Wow, that's an odd looking plane! I'm tempted to say the real reason is that rectangular fuselage planes are ugly ;-) 2. Seriously though, even taking aerodynamics out of the equation, spherical pressure vessels are quite rare. Flick through any industrial compressor catalog and you'll see all the tanks are cylindrical, because of the ease of fabricating cylindrical  sides and the difficulty of fabricating hemispherical ends. The only difference is the aspect ratio is 2-3 times shorter than a typical plane.

@steveverrill I wouldn't say ugly. I do have an aircraft design that has a rectangular fuselage and looks really cool looking when I picture it in my head.

@steveverrill: I don't know about spherical pressure vessels being that rare. Consider natural gas tankers and natural gas tanks for examples. Granted, those are big tanks rather than something you'd see in a compressor catalogue but there's still quite common.

@muistooshort Liquefied natural gas tanks are spherical to reduce surface area and therefore insulation. Strictly speaking they aren't pressure vessels, as they operate at ambient pressure (and -162C temperature.) Methane has a critcal point of -83C and therefore cannot be liquefied at ambient temperature. A spherical pressure vessel offers 25% theoretical material saving over an infinitely long, thin cylinder. In practice it's rarely worth it if pressure is the only consideration.

@LevelRiverSt: In practice, infinitely-long structures are rarely practical...  :P

Drag has little to nothing to do with it.
The primary reason why the fuselage is circular (or elliptical) shaped is that the cabin is pressurised.
This means that, mostly during cruise, the interior of the fuselage has an higher pressure than the outside atmosphere. The circular (or roughly circular) shape allow the fuselage to avoid blowing up like a baloon with minimal amount of material, minimizing the overall weight of the aircraft. A square fuselage would break apart at the corners due to stress concentration. A circular shape do not have corners were the tensile stress can concentrate.

Drag has insofar to do with it that otherwise aircraft fuselages would be spheres. The cylinder of the same volume causes much less drag when moved through air along its longitudinal axis. Plus, there are more window seats possible if you take a cylinder ;-)

@PeterKämpf I agree, but the question is "circle vs square section", not about the 3D shape

@PeterKämpf More space to put your bags in a square shaped. And also more cabin width.


text:
Why are visual approaches (in the US) preferred by US pilots, but not European pilots?
I listen to ATC a lot and often hear airliners cleared for visual approaches in the USA. Interestingly, if it's European airliner pilots they deny the visual approach and request ILS even if they are in an emergency and probably should land ASAP. Why is that? Are European pilots not used to hand flying? I assume pilots flying, for example, A380, should have extremely good piloting skills. What is the problem with doing a simple visual approach?
I also haven't heard yet from ATC to clear an airliner for a visual approach in Europe.
Here is the audio source (via YouTube): 30% of time is spent dealing with turning ILS on for 31L.

I'm not sure this question will remain open without edits because European pilots do visual approaches all the time, though the weather at home is probably less amenable to it. Is it truly less often than other airlines when conditions permit? If you've heard one insist on an ILS during an emergency when they should land ASAP you should back that up with a source. But it's true that some airlines have been too conservative and not let their pilots practice visual approaches - the Asiana 214 captain who crashed at SFO had rarely flown them.

I added the source.

The same question can be also probably reversed: Why are visual approaches (in the EU) preferred by EU pilots, but not US pilots?

Since your question explicitly mentions emergency situations:
Especially during time-critical emergency landings, the workload of the flight crew is at a higher level anyway. The answer by ymb1 already explains that familiarity with the airport surroundings is usually lower for foreign pilots. Add to the fact that at the end of a long-haul flight, fatigue levels may be higher for those crews. In this case, performing an instrument approach instead of a visual is one more technical aid (which you can easily make use of) to ensure an early stabilized approach, especially when your mindset is rather in hurry due to the emergency.

Another factor in an emergency landing is you may be landing at an unfamiliar airport.

Part of the issue may be that airline companies have specific rules/regulations to what aircrew are allowed to do. In Europe it is quite common for airline companies to only allow their aircrews visual approaches at their home bases (e.g. Amsterdam for KLM) or, in case the company uses several hubs, on those hubs.
There's a thin line between allowing visual approaches to keep up training levels for aircrews and forcing instrument approaches to reduce risk, potential additional costs (imagine the costs of a go-around during practicing visual approaches) and loss of throughput from an ATC perspective.

"and loss of throughput from an ATC perspective." Throughput is less with instrument approaches, not more.

First, background info. A visual approach can have various meanings. In the case of airlines it does not convert an IFR flight to VFR nor cancel the flight plan. What ATC is doing [in the USA] is asking a pilot "do have the runway in sight?" or "traffic 4 miles ahead and 1000 feet below, B737, do you have it in sight?", if the pilot says no than ATC maintains positive control and minimum radar separation, if the pilot says yes then ATC can issue a visual approach either directly if the runway is in sight or with "follow that plane, maintain visual separation, cleared to land runway 35R" even if the runway is not yet visible. As the pilot is maintaining separation (with a specific aircraft only) the radar minima are no longer in effect and reduces ATC workload so they can focus on other problems like looking for aircraft that are off course, and it allows much closer spacing and landing. Tower based visual separation is often used for departures before radar minima are achieved, this is a controller in the tower looking at both planes out of the window.
Now why do American pilots favor visual separation and clearance?
A cultural difference, in part due to the supply of pilots and general aviation, in part due to the general culture of the country. The majority of general aviation is in north America and so US airline pilots are often sourced from general aviation pilots that are accustomed to visual flight procedures. The USA also has traditionally had a very large supply of military pilots, who are even more accustomed to adapting to non-standard conditions and visual separation.(like in flight refueling) Often military convoys are simply given block altitude corridors by ATC and the pilots fly as they like within that block separating themselves.
With FAA regulations, while under positive ATC radar separation both the pilot and controller are more at risk of a regulation violation if minimum separation is not maintained. There is no explicit minimum for two planes under visual separation.(radar separation still applies to other traffic)
Airline companies outside of the USA, due to a lack of general aviation and smaller military, tend to train pilots "ab-initio". That is complete training from the beginning, often targeted at a specific plane and airline procedures. This is more narrowly focused than typical American training; this is efficient but some of the programs may lack breadth. I tend to think this focus can make a very good co pilot in less time but maybe is not as good for captains.(only an opinion and not a strong opinion) Funny enough many of these airlines have their training programs in the USA for reduced cost and may use US instructors, but it is not typical US curriculum.
Now for company culture, non-USA airlines often encourage full use of automation to avoid pilot deviation from standards. This includes using radar separation rather than visual, computer limited flight controls(Airbus "normal law"), and heavy use of autopilot even at lower altitudes. This has the side effect of more pilots loosing the ability to handle alternate situations. So you have reduced problems created by pilot judgment but may also reduce pilot judgment when there is a problem. Air France 447 is the most recent example with a full investigation report.(LionAir610 may also be an example based on the preliminary report, but the investigation is still in progress.) I do not know the legal responsibility in each country, maybe airline company, maybe pilot, etc.
On the US side, the pilot in command is legally responsible for the whole flight from from preflight log review and general aircraft inspection all the way to engine shutdown and unloading. As such the pilot has final authority to accept or refuse any ATC instruction. Though this has some limits; if you say yes to do something and then do something different this is a "pilot deviation" and may require paperwork to explain. US ATC often asks pilots to "state intentions" if the pilot contacts them with a problem, that is the pilot tells ATC what the pilot is going to do rather than asking for permission. Basically you may hear pilots outside the USA asking permission to maneuver or land, even in an emergency; in the USA pilots are trained to take any action needed to get the plane on a runway in one piece and to inform ATC is second priority(helpful but not essential).

Visual vs. ILS/RNAV/Whatever approaches are not what determines whether the crew is hand flying, that is for sure.  All instrument rated pilots are tested on and regularly required to hand fly instrument approaches, and some instrument approaches actually do not allow for autopilot coupling below a certain altitude (that doesn't mean pilots don't cheat, but they are breaking the rules if they do).  Further, a good number of pilots will still follow an instrument approach down much of the way to the runway anyway, given that visual clearances generally aren't given until the airport is in sight.  The real difference is that visual approaches are given out once ATC knows the airport is in sight.  That doesn't mean the crew can't still fly the instrument approach to minimums, it just means that ATC can keep increase the stream of arrivals with reduced spacing.
Also, I don't hear Lufthansa, British Airways, Edelweiss or even JAL denying the visual at SAN.  They could, but there really isn't a need.  Of course, there is no ILS on Runway 27, so that affects things.


text:
Where can I find more information about that glass board in old aircraft carrier operations centers?
When I was a kid, I used to read this comics about aircraft pilots in the 50's, and in the operations center of their aircraft carrier, they had operators using markers on a glass wall to keep track of operations. Any idea how that was called and where I can find pictures of it? Is it still in use today, or is it now all computerized?

May have been the Combat Information Center

Still in use in 2006.

The "glowing summary plot" the CIC looks quite close! Can you make it an answer out of it? Do you have various pictures?

There is an example in the USS Midway. It's right next to the Airboss seat, and I hoped I had a picture of it from my visit, but it seems I didn't.

The one I'm looking for was a display that's just a vertical piece of glass that one operator would write onto on one side, and others could look at on the other side to understand where the airplanes were.

@mins Not what I was thinking of. This would have been in the 'tower'.

I don't agree that this is off-topic, we already have answered questions about ATC radar displays, this one just happens to be military related.

This is what you are after. Another one. It seems to be known also as a vertical summary plot.

@mins - YES! Thanks! Can you make an answer out of this, rather than just a comment?

I'm sure someone more informed than me will write this answer.

If I recall, I think the board you're talking about is in the CATCC (Carrier Air Traffic Control Center) room on a CVN aircraft carrier. I was an Electronics Tech on the USS Abraham Lincoln and remember seeing this board there. I've been trying to Google some info, but can't come up with anything ... likely because the space is usually classified and sanitized before media is allowed in. By the way, this is not where the air boss is (he's in the conning tower, CATCC is below the flight deck).